Field of the Invention
The present invention relates to a piezoelectric device, which is a sintered body including a main body part including a part made of a piezoelectric material, a top surface electrode that covers at least a part of a top surface part of the main body part, a bottom surface electrode that covers at least a part of a bottom surface part of the main body part, and a side surface electrode that covers at least a part of a side surface part of the main body part and connects the top surface electrode to the bottom surface electrode. The piezoelectric device is also referred to as a piezoelectric/electrostrictive device.
Description of Related Art
This type of piezoelectric device has been developed actively for a position control device for an optical lens (for example, an ultrasonic motor for auto-focusing or zooming of a camera), a position control device for a read and/or write element for magnetic information or the like (for example, an actuator for a magnetic head of a hard disk drive), a sensor for converting mechanical vibration into an electrical signal, or the like (see, for example, JP 2006-100805 A and JP 2002-359148 A).
The above-mentioned piezoelectric device is produced in accordance with the following procedure, for example. A state “prior to sintering” is hereinafter expressed by prefixing “green” to a name of a corresponding member.
First, on a tabular substrate, there is formed one large tabular green compact including parts corresponding to the piezoelectric devices prior to sintering (hereinafter referred to as “green piezoelectric device corresponding parts”) that are aligned at predetermined intervals.
Next, a machining process such as a cutting process or a punching process is performed on the large green compact placed on the substrate. As a result, there is obtained a state where a plurality of green piezoelectric device corresponding parts are placed at predetermined intervals on the substrate. Each green piezoelectric device corresponding part includes a green main body part that corresponds to a main body part, and a green top surface electrode and a green bottom surface electrode that are formed on top and bottom surfaces of the green main body part and correspond to a top surface electrode and a bottom surface electrode, respectively.
Next, at a predetermined place of a side surface of each green piezoelectric device corresponding part (namely, a surface exposed by the machining process), a green side surface electrode that corresponds to a side surface electrode is formed so as to connect the green top surface electrode to the green bottom surface electrode. Then, the plurality of green piezoelectric device corresponding parts are sintered. As a result, the plurality of piezoelectric devices (after sintering) can be obtained in the same process.
Here, as described above, in a case of adopting the method of obtaining the plurality of green piezoelectric device corresponding parts by performing a machining process such as a cutting process or a punching process on one large tabular green compact, there may occur such a situation that a sharp angle shape or a burr is generated at an intersection part between the top surface and the side surface of the obtained green piezoelectric device corresponding part (at an edge of the top surface).
In a state where the above-mentioned situation has occurred, if the step of forming the green side surface electrode is carried out, there is a tendency that a film thickness of the green side surface electrode becomes relatively small at a “part in a vicinity of a boundary between the green top surface electrode and the green side surface electrode.” Therefore, after sintering, there is a tendency that a film thickness of the side surface electrode becomes small at a part in a vicinity of a boundary between the top surface electrode and the side surface electrode. As a result, there may occur a problem in that a conduction failure is liable to occur between the top surface electrode and the side surface electrode.
In order to deal with this problem, grinding or the like may be performed on the edge of the top surface of the green piezoelectric device corresponding part before the step of forming the green side surface electrode so as to remove the above-mentioned sharp angle shape or burr. However, if a size of the piezoelectric device is very small, it is very difficult to perform the grinding or the like.